Tycho Brahe (1546–1601), usually referred to as Tycho (the Latinization of his given name Tyge), was a Danish nobleman who chose to pursue his passion for astronomy rather than the career of statesman that his birth destined him for. He spent his most productive years as an astronomer on the island of Hven in the Øresund (now called Ven and part of Sweden since 1658), granted to him in fee by king Frederick II of Denmark. On the island, thanks to the financial support of the king, Tycho built Uraniborg, a residence fitted with observatories and other features designed for scientific work, and later Stjerneborg, a partially underground observatory.

Tycho Brahe

Tycho Brahe

Dedicated to achieving the highest data quality, Tycho designed new astronomical instruments and supervised their construction. With his assistants, he gathered a wealth of observations of the stars, sun, moon, and planets with an accuracy that far surpassed anything available at the time.

Tycho's fortunes changed after the death of king Frederick. The new king Christian IV didn't share his father's favorable disposition towards the astronomer and several events conspired to force Tycho to leave the island and then Denmark in 1597. He ended up imperial astronomer at the court of Rudolph II in Prague where he was joined by Johannes Kepler, forced to leave his position in Graz due to religious tensions. After Tycho's death in 1601, Kepler succeeded him as imperial astronomer. He inherited Tycho's observations of the planets that enabled him to discover his famous laws of planetary motion.

For details on Tycho's life and work, refer for instance to Kitty Ferguson's book [2], the more detailed biography by J. L. E. Dreyer [8], or the comprehensive and more recent biography by Victor Thoren [5].

This page focuses on the star catalog that resulted from Tycho's measurements of star positions. Two main versions of the catalog exist.

☞ One version, containing 777 entries, is included in the first volume of Tycho's Astronomiæ Instauratæ Progymnasmata [12, pp. 258–272], published posthumously by Kepler in Prague in 1602. There also exists a 1610 edition [12], published in Frankfurt, where the star catalog exhibits some differences with the 1602 version. The 1602 version is reproduced in Tome II of Dreyer's edition of Tycho's complete works [6, pp. 258–280].

☞ Shortly before leaving Uraniborg, Tycho rushed the completion of the catalog to 1000 stars, the benchmark number set by Ptolemy whose catalog contains 1028 entries. Due to the chaotic circumstances surrounding the move, the extended 1004 entries catalog is not up to the standard of quality of the smaller one. Nevertheless, Tycho had elegant manuscript copies made of it and sent to potential new patrons. This catalog is reproduced in Tome III of Dreyer's edition of Tycho's complete works [5, pp. 344–373].

Kepler included a version of Tycho's long catalog in his last major work, Tabulæ Rudolphinæ [10, pp. 105–114]. This version is reproduced in Francis Baily's The Catalogues of Ptolemy, Ulugh Beigh, Tycho Brahe, Halley, Hevelius, Deduced from the Best Authorities [8, pp. 127–165].

John Flamsteed included a copy of Tycho's catalog in the third volume of his Historia Cœlestis Britannica [9, pp. 24–45]. This appears to be a version of the long catalog, although some of the constellations are restricted to the stars included in the short one. Flamsteed's own star catalog includes cross-references to Tycho's.

More recently, Dennis Rawlins in DIO 3 [3] published a version of the manuscript catalog, with some corrections, and critically examined it, going back to Tycho's original observations in order to explain inaccuracies. He also showed in great detail in DIO 2.1 [4] that some of the last entries added to the catalog in order to reach the magic count of 1000 have not been directly observed but adapted from Ptolemy's catalog.

Tycho's catalogs have already been digitized by F. Verbunt and R. H. van Gent [1] from Dreyer's and Kepler's copies and made available as VizieR's catalog J/A+A/516/A28.

I have independently digitized a few versions Tycho's catalog and made the results available on this page. I copied Tycho's manuscript catalog from Dreyer [6], the 777 star catalog from the 1602 edition of Progymnasmata [13], the 1610 edition of Progymnasmata [12], and from Dreyer [7], Kepler's version from Tabulæ Rudolphinæ [11] and Baily's collection [9], and Flamsteed's version from Historia Cœlestis Britannica [10].

Constellations in Tycho's catalogs

Tycho's catalog covers most of Ptolemy's constellations. Ara, Corona Australis, Lupus, and Piscis Austrinus, invisible or barely visible at Tycho's latitude, are absent. Centaurus is represented by only 4 stars in the long versions. On the other hand, Tycho acknowledges Antinous and Coma Berenices, introduced by Caspar Vopel in 1536, as separate constellations.

In the manuscript and Progymnasmata versions, the zodiacal constellations come first, then the northern, then the southern. In Kepler's version, the northern come first, then the zodiacal and the southern.

Centaurus is absent from the Progymnasmata version. Antinous follows Aquila. Coma Berenices appears between Auriga and Ophiuchus in the Progymnasmata version, but between Boötes and Corona in the manuscript version and as the last northern constellation in Kepler's version. Otherwise, each group follows Ptolemy's constellation order.

Catalog data

The files tycho_*.dat contain the versions of Tycho's star catalog. For completeness and out of respect for the originals, they include the star descriptions in Latin. The descriptions are UTF8-encoded for accented and other non-ASCII characters.

The file notes.dat gives general notes about all versions. The other notes files describe issues specific to various versions.

File name Explanation
ReadMe File descriptions
tycho_m.dat Manuscript catalog of 1004 stars from Dreyer
tycho_t.dat Catalog of 777 stars from Progymnasmata (1602 edition)
tycho_y.dat Catalog of 777 stars from Progymnasmata (1610 edition)
tycho_d.dat Dreyer's version of the Progymnasmata catalog
tycho_k.dat Catalog of 1005 stars from Kepler's Tabulæ Rudolphinæ
tycho_b.dat Baily's version of the Tabulæ Rudolphinæ catalog
tycho_z.dat Flamsteed's version of the long catalog
notes.dat General notes on Tycho's catalogs
notes_m.dat Notes on the manuscript version from Dreyer
notes_t.dat Notes on the Progymnasmata versions
notes_k.dat Notes on the Kepler versions
notes_z.dat Notes on Flamsteed's version

The ReadMe file describes the common file format of the catalog files according to the conventions for catalog descriptions of the VizieR service, with the following caveat: the VizieR standard and their Anafile package for automatic validation only accept ASCII input. Therefore, to properly match the file descriptions and pass automatic validation, the catalog files should be stripped of file descriptions, which can easily be accomplished with command-line tools. To avoid clutter, I haven't included stripped versions.

The versions of the Progymnasmata catalog differ from each other. Some position and magnitude values are missing in the 1602 version, which is clear in the [BSL02] copy (see reference [13]). In the [LOC02] copy, these values appear to have been added by hand. The missing values are supplied in an Errata Typographica section at the end of the book, and sometimes differ from the [LOC02] handwritten values. I have followed the errata. The 1610 version has no missing values (although the errata section hasn't been updated), but differs from the 1602 version in quite a few places. Dreyer's version shows a single non-documented difference with (my interpretation of) the 1602 version. All the differences are described in notes_t.dat file and formalized in the corrections files.

The Kepler and Baily versions differ from each other as well. Baily has corrected some obvious errors in Kepler's version but also introduced typos of his own. The differences are described in notes_k.dat as well and formalized in the corrections files described below.

Besides omitting some stars from the manuscript version, Flamsteed's version shows several differences in positions or magnitudes. They are mentioned in notes_z.dat.


The Progymnasmata and manuscript versions start with the zodiacal constellations, then the northern and southern ones. Kepler's version starts with the northern constellations, then the zodiacal ones, then the southern.

The catalog covers Ptolemy's constellations except the southernmost ones (Lupus, Ara, Corona Australis, Piscis Austrinus), invisible or barely visible at Uraniborg's latitude. A handful of Centaurus stars are present as an afterthought in the manuscript and Kepler versions. Ptolemy's order is respected within each group (northern, zodiacal, southern).

In addition, the catalog features the new constellations Coma Berenices and Antinous (previously part of Leo and Aquila respectively), introduced by Caspar Vopel on a celestial globe in 1536. Coma Berenices figures between Auriga and Ophiuchus in the Progymnasmata version, but between Boötes and Corona Borealis in the manuscript version, and as the last northern constellation in Kepler's version.

Some constellations are designated by ancient or alternative names. These cases are collected in the following table.

Standard name Tycho Kepler
Ursa Minor Ursa Minor, Cynosura Ursa Minor, Cynosura
Ursa Major Ursa Maior, Helice Ursa Maior, Helice
Boötes Bootes seu Arctophylax Bootes, Arctophylax
Corona Borealis Corona Borea, Gnossia Corona Borea
Hercules Hercules, En Gonasi Engonasi, Hercules
Lyra Lyra, Vultur Cadens
Cygnus Olor, Cygnus
Cassiopeia Cassiopea
Auriga Erichthonius Auriga, Heniochus, Ericthonius
Ophiuchus Ophiuchus, Serpentarius
Serpens Serpens Ophiuchi
Sagitta Sagitta sive Telum
Aquila Vultur Aquila seu Vultur Volans
Equuleus Equuleus, Equi Sectio
Pegasus Pegasus, Equus Alatus
Triangulum Triangulus Triangulus, Deltoton
Cetus Cete Cete
Canis Minor Canis Minor, Procyon
Argo Navis Argus
Centaurus Centaurus, Chiron

Nebulous objects

The entries marked nebulous in Tycho's catalog are collected in the following table. Of these, only Cnc 1 corresponds to an actual non-star object, although the position given by Tycho corresponds very accurately to the individual member HR 3428 of this cluster.

TIDModern designation
Cap 510Cap π
Cap 612Cap ο
Cap 8 7Cap ρ
Cnc 1Praesepe, M44, NGC 2632
Her20HR 6641


The correction files listed below serve two purposes. The first one is to reconcile the versions of the Progymnasmata catalog (choosing the 1602 version from Progymnasmata with errata as reference), and to reconcile Kepler's and Baily's versions of the Tabulæ Rudolphinæ catalog (choosing the version from Tabulæ Rudolphinæ as reference).

File name Explanation
corrs_m.dat Corrections to the manuscript catalog from Dreyer
corrs_t.dat Corrections to the Progymnasmata catalog (1602 edition)
corrs_y.dat Corrections to the Progymnasmata catalog (1610 edition)
corrs_d.dat Corrections to Dreyer's version of the Progymnasmata catalog
corrs_k.dat Corrections to the Tabulæ Rudolphinæ catalog
corrs_b.dat Corrections to Baily's version of the Tabulæ Rudolphinæ catalog

The second purpose is to correct obvious position errors (wrong longitude zodiac sign or latitude sign in most cases), which Baily has done in many cases while introducing typos of his own, so that they don't make the maps on the next page (which use the corrected data) messier than they need to be.

Each entry in the correction files mentions the star designations and the corrected field values; they don't repeat unaffected field values. Consequently, they don't contain full catalog entries but rather overlays to catalog entries. They still conform to the same format as the catalog files and are described in the ReadMe file.

Star designations

Up to 4 designations are assigned to every entry in the catalog files: the sequence number mno in the manuscript catalog, the sequence number tno in the Progymnasmata catalog, the sequence number kno in Kepler's catalog, and the combination tid of a constellation abbreviation tcon and a sequence number tnum within the constellation. These designations are not present in the originals (except Baily's version) but are more convenient than the star descriptions to identify stars uniquely.

The catalog files are sorted by the global sequence number corresponding to their source. The sequence numbers tnum by constellation are somewhat arbitrary: they follow the order of the catalogs when possible, but there are some variations between versions and these numbers may not appear sequential in some versions.

All the entries in the Progymnasmata catalog are contained in the manuscript and Kepler versions, but both the manuscript and Kepler versions have a handful of entries absent from the others. These cases are described in notes_m.dat. As a result, the combination tid of constellation abbreviation and number within the constellation is the only one of the designations that can serve as global primary key for all versions.

Baily's version uses the kno and tid designations explicitly in the same manner. VizieR catalog J/A+A/516/A28 has a similar numbering scheme. My mno and tno are equivalent to theirs, but their version of kno and tid do not exactly match mine or Baily's. The main reason is that, for some lines of Kepler's catalog, they have decided differently whether to treat them as separate entries. They end up with 1004 entries in Kepler's version and Baily with 1005. I have followed Baily.

Star identifications

Dreyer's version of the manuscript catalog and Baily's version of Kepler's catalog assign Bayer, Flamsteed, or other (Piazzi, Groombridge) designations to Tycho stars. Flamsteed's version adds Bayer letter assignments.

I have captured these identifications in the following files, described in ReadMe and subject to automatic validation.

File name Explanation
cross_m.dat Star identifications according to the manuscript catalog from Dreyer
cross_b.dat Star identifications according to Kepler's version from Baily
cross_z.dat Star identifications according to Flamsteed's version Tycho's catalog
cross_f.dat Star identifications extracted from Flamsteed's catalog
dups.dat Possible duplicate entries

Flamsteed's own catalog has references to Tycho's (Kepler's version apparently, due to the presence of Sgr 1 and Sgr 2). The file cross_f.dat, generated from Flamsteed's catalog, orders these implicit Flamsteed number and letter assignments according to Kepler's version of Tycho's catalog.

Letter assigments have shifted over time and should be interpreted in their context. In particular, Flamsteed uses the additional letters that he introduced in his own catalog and Baily, if he continued for Tycho's catalog what he did for Ptolemy's, uses the letters he retained in his enhanced version of Flamsteed's catalog in An Account of Flamsteed (reference on the Flamsteed page).

Duplicate entries

The file dups.dat, described in ReadMe, lists pairs of possible duplicate entries found in Tycho's catalogs. An equal sign flags pairs considered duplicates by Rawlins in [3] (footnote 77), and the pair Oph 6 | Oph 33 mentioned in [4]. The other close pairs, flagged by a star, may not be true duplicates due to erroneous catalog positions.

On the other hand, there may be duplicates that don't appear in the file because erroneous catalog positions place the stars far from each other. Rawlins [3] considers the pairs Cyg 11 | Cyg 25 and Per 30 | UMi 13 (mno 554 | 568 and 644 | 348 respectively) as duplicates.


[1] F. Verbunt & R. H. van Gent, Three editions of the star catalogue of Tycho Brahe, Astronomy & Astrophysics 516, A28 (2010).

[2] Kitty Ferguson, Tycho and Kepler: The Unlikely Partnership that Forever Changed our Understanding of the Heavens, New York: Walker & Company, 2004.

[3] Dennis Rawlins, Tycho’s Star Catalog, DIO, Vol. 3, October 1993.

[4] Dennis Rawlins, Tycho 1004-Star Catalog's Completion Was Faked, DIO, Vol. 2, No. 1, April 1992.

[5] Victor E. Thoren, The Lord of Uraniborg: A Biography of Tycho Brahe, Cambridge University Press, 1991.

[6] John Louis Emil Dreyer, Tychonis Brahe Dani Scripta Astronomica, Tomus III, Hauniae in Libraria Gyldenlaliana, 1916.

[7] John Louis Emil Dreyer, Tychonis Brahe Dani Scripta Astronomica, Tomus II, Hauniae in Libraria Gyldenlaliana, 1913.

[8] John Louis Emil Dreyer, Tycho Brahe: a picture of scientific life and work in the sixteenth century, Edinburgh : Adam & Charles Black, 1890.

[9] Francis Baily, The Catalogues of Ptolemy, Ulugh Beigh, Tycho Brahe, Halley, Hevelius, Deduced from the Best Authorities. With Various Notes and Corrections, and a Preface to Each Catalogue. To Which is Added the Synonym of each Star, in the Catalogues of Flamsteed of Lacaille, as far as the same can be ascertained. Memoirs of the Royal Astronomical Society, Vol. 13, London, 1843. Also available here.

[10] John Flamsteed, Historia Cœlestis Britannica, Tribus Voluminus contenta. Volumen Tertium, London, 1725.

[11] Johannes Kepler, Tabulæ Rudolphinæ, Ulm: Jonas Saur, 1627.

[12] Tycho Brahe, Astronomiae Instauratae Progymnasmata, Frankfurt: Gottfried Tampach, 1610. I consulted the online versions of copies at e-rara [ETH10], the Bavarian State Library [BSL10], and the Lyon Public Library [LPL10].

[13] Tycho Brahe, Astronomiae Instauratae Progymnasmata, Uraniborg & Prague, 1602. I consulted the online versions of copies at the Library of Congress [LOC02] and the Bavarian State Library [BSL02].


  • This research has made use of the VizieR catalogue access tool, CDS, Strasbourg, France. The original description of the VizieR service was published in A&AS 143, 23.
  • This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France.
  • Illustration: Tycho Brahe. Line engraving after T. Gemperlin, 1586. Credit: Wellcome Collection. CC BY